This application describes a collaborative project on the relationship between tumor necrosis factor (TNF) and the E3 transcription unit of adenovirus. TNF is a monokine secreted by cells of the monocyte/macrophage lineage in response to inflammatory stimuli. It has diverse biological functions which include regulation of cells involved in immunity and inflammation, cytolysis of certain tumor cells, and inhibition of intracellular pathogens. Notably, a major function of TNF apparently is to combat virus infections. We have found that TNF lyses cells infected by human group C adenoviruses with deletions in early region E3. Uninfected cells and cells infected by wild type adenovirus are not lysed. These results indicate that adenovirus renders cells susceptible to lysis by TNF, and that a product of region E3 protects against lysis. Using a variety of E3 deletion mutants, we have shown that protection against TNF is conferred by a 14.7K protein encoded by region E3. We have prepared a strong antiserum against this proteins and have determined that it is an abundant protein which is conserved in at least three of the seven groups of human adenoviruses. We hypothesize that the 14.7K protein evolved to protect virus infected cells against lysis by TNF. Our major goals are to understand in molecular terms how the 14.7K protein protects against TNF, and how adenovirus induces susceptibility to lysis by TNF. This basic understanding eventually should help us to develop strategies for employing TNF as an anti-viral agent. We also hope to correlate the function of the 14.7K gene as well as other E3 genes with the pathogenicity of different adenovirus isolates and serotypes. Our specific aims are outlined as follows: (I) The 14.7K protein will be characterized and purified. (II) The function of the 14.7K protein in counteracting TNF lysis will be studied by analyzing 14.7K mutants, and by microinjecting the 14.7K protein into cells. (III) The gene(s) that induce susceptibility to TNF lysis will be mapped using virus mutants.